Another day, another piece of bad news for Facebook. This time, it involves WhatsApp CEO Jan Koum, who has announced his decision to leave the company he co-founded and step down from Facebook’s board of directors. According to the Washington Post, Koum’s announcement follows clashes with Facebook over data privacy and WhatsApp’s business model.

Koum and Brian Acton founded WhatsApp back in 2009. They eventually sold the popular application to Facebook for $19 billion in 2014, at which point Koum negotiated a role on Facebook’s board. Acton quit the company last year to start his own non-profit.

“It’s been almost a decade since Brian [Acton] and I started WhatsApp, and it’s been an amazing journey with some of the best people. But it is time for me to move on,” Koum wrote on his Facebook profile.

“I’m taking some time off to do things I enjoy outside of technology, such as collecting rare air-cooled Porsches, working on my cars and playing ultimate frisbee. And I’ll still be cheering WhatsApp on – just from the outside.”

Koum and Acton had built WhatsApp as a privacy-focused communications app, and the pair vowed that the Facebook acquisition wouldn’t compromise their vision. The rollout of end-to-end encryption in 2016 seemed to back up their promise, but there was concern when the company started sharing more user data, including phone numbers, with its new parent later that same year.

According to “people familiar with internal discussions,” the introduction of end-to-end encryption was a point of contention for Facebook. The social network’s execs wanted to ensure businesses could use their tools on the messaging service, and WhatsApp executives believed this meant weakening encryption. Facebook had eliminated WhatsApp’s $0.99 annual subscription and allowing businesses to chat with customers was one of the ways it wanted to monetize the service.

While the Cambridge Analytica scandal wouldn’t have helped matters—and led to Acton tweeting his support for the #deletefacebook campaign—Koum reportedly made his decision to leave before the revelations. The Post wrote that he was ultimately “worn down by the differences in approach.”

The first comment on Koum’s Facebook post comes from the company’s CEO, Mark Zuckerberg. “I’m grateful for everything you’ve done to help connect the world, and for everything you’ve taught me, including about encryption and its ability to take power from centralized systems and put it back in people’s hands. Those values will always be at the heart of WhatsApp.”